We want to find the axis of symmetry of the function;

STEP 1:
The equation for the axis of symmetry of a line is given as;

From the equation, a = 6 and b = -3, so,
STEP 2: Insert the values of a and b into the equation to obtain;

CONCLUSION:
Therefore, we see that the axis of symmetry is the line;
I believe it is C hope this helps
The labeled angle is what's called an inscribed angle. There's a theorem (fittingly called the inscribed angle theorem) that says the measure of this angle is half the measure of the circular arc that it subtends.
In this case, the angle is subtended by an arc measuring 180°. So
(4x + 6)° = 1/2 • 180°
4x + 6 = 90
4x = 84
x = 21